Title of Invention : METHOD OF AND APPARATUS FOR

OBTAINING A SOIL SAMPLE

Technical Field

[0001 ] This invention relates to a method of and apparatus for obtaining a soil

sample particularly but not exclusively for analysis to obtain an indication of the carbon content of the soil sample and soil from which the sample is taken.

Background Art

[0002] Carbon dioxide in the atmosphere generally considered to be caused by the use of fossil carbon fuels which forms an insulating gas layer or blanket which determines the average temperature of the Earth's biosphere. Due to the build up of the carbon dioxide layer in the atmosphere, the biosphere is overheating as a result of the "greenhouse" effect of this layer thereby producing global warming. Reducing the rate at which the layer is increasing in thickness for example by substantially reducing the rate of use of fossil carbon fuels would be insufficient in itself to reduce this heating effect or stop progressive global warming.

[0003] The only current practical, economic and efficient way of removing

accumulated excess greenhouse gasses is to sequester carbon dioxide in agricultural soils. In this process carbon in atmospheric carbon dioxide is converted into carbon in organic matter in the soil known as soil humus.

Production of soil humus which makes poor soils fertile reduces the need to use strong agricultural chemicals which tends to hinder rapid formation of fertile soil.

[0004] To encourage the use of carbon dioxide sequestration, a scheme has been proposed whereby farmers are paid remuneration based on the tonnage of the carbon dioxide removed from the air by converting it into soil humus or organic matter. One disadvantage of this scheme is that it is difficult to measure organic carbon content in soil.

[0005] Current methods for measuring carbon content in the soil typically involve the taking of a small sample of soil and testing that sample using chemical analysis or heating in an oven to provide an indication of carbon content in a particular area. The results from these tests are then extrapolated to produce a measure of carbon content over a whole area from which the sample is taken. The current methods are not particularly effective or accurate.

[0006] In my International Patent Application No. PCT/AU2013/ 00151 1 , I disclose an improved method of and apparatus for obtaining an indication of carbon content in soil. It is necessary however, whatever means are used for obtaining an indication of carbon content of soils, that the correct protocol be adopted to ensure that a relatively accurate assessment of carbon content in the soil can be obtained particularly as remuneration in a program which rewards carbon dioxide sequestration is based upon a person seeking such remuneration being able to provide relatively accurate figures.

[0007] To date there has not been proposed, as far as the applicant is aware, a

method and apparatus which enables standardised soil samples for carbon content analysis to be obtained from a particular area of ground.

[0008] The present invention aims to address the above problems and in particular to provide a method and apparatus for obtaining a soil sample which ensures that an accurate and standardised sample may be obtained for subsequent testing. Whilst the method and apparatus of the invention are particularly suited to obtaining a soil sample for carbon content calculations, the method and apparatus may be applied to obtaining soil samples for other purposes.

Summary of Invention

[0009] The present invention thus provides in one preferred aspect a method of

obtaining a sample of soil from a selected area of ground, said method

comprising the steps of providing a hollow tubular body, providing a sample collection means having an opening therein adapted to freely receive said tubular body, arranging said collection means flat on said ground area and positioning said tubular body in an upright attitude with the lower end thereof arranged within said opening, inserting an auger into said tubular body rotating said auger and causing said tubular body and auger to advance into the ground whereby soil within said tubular body is caused to move relatively upwardly and out of the upper open end of said tubular body to collect on said sample collection means. [0010] The method of the invention may also include the steps of removing the auger and tubular body from the soil after the tubular body is advanced fully into the ground and closing the opening in the collection means such that the sample of soil can be retained on the collection means. The method may also include the step of locating a soil lifting device beneath any remaining soil or materials in the tubular body prior to its removal from the ground and moving the device longitudinally thereof to lift the remaining soil or materials from the body for addition to soil retained on the collection means.

[001 1 ] In a further preferred aspect, the present invention provides apparatus for obtaining a sample of soil from a selected ground area, said apparatus

comprising a hollow tubular body, a sample collection means adapted to be located flat on said ground, said sample collection means having an opening therein adapted to freely receive said tubular body when the latter is arranged in an upright attitude such that said tubular body can be advanced therethrough into the ground, and an auger adapted to be received within said tubular body, said auger when rotated causing soil within said tubular body to move relatively upwardly and out of the upper open end of said tubular body to collect on said sample collection means.

[0012] Preferably, the tubular body has a collar at its upper end adapted to

cooperate with the sample collection means to act as a stop to limit movement of the tubular body into the ground. The collar suitably includes an outwardly and downwardly inclined surface in a frustoconical configuration for directing in use collected soil exiting from the upper end of the body downwardly onto the sample collection means.

[0013] Preferably a pair of arms are fixed to the tubular body and extend radially

therefrom. Suitably, one of the arms can act as a stop to rotation of the tubular body. The one of the arms suitably is adapted to abut the leg of a user in use so as to prevent rotation of the tubular body.

[0014] To assist penetration of the tubular body into the ground, the operative lower or leading end thereof is of a tapered or sawtooth configuration, the latter comprising a plurality of teeth arranged around the end of the tubular body. When the tubular body is rotated and a downward force applied to the body, the teeth will penetrate the ground permitting the body to move downwardly into the soil. [0015] Preferably a skirt is associated with the tubular body, the skirt being adapted to be positioned to surround the upper end of the tubular body and being adapted to direct soil exiting the upper end of the tubular body outwardly and downwardly onto the sample collection means. The skirt suitably includes a pair of skirt members, the skirt members cooperating to surround the upper end of the tubular body. The skirt members are suitably formed of a flexible or pliable material such as a hard wearing fabric e.g. canvas or a canvas-like material. The skirt alternatively may comprise a single skirt member in a tubular or annualar configuration which can be mounted to the tubular body in a position surrounding the upper end of the tubular body.

[0016] Preferably where the skirt comprises a pair of skirt members, the respective skirt members are adapted to be mounted to the arms so that they oppose each other. Each skirt members is suitably mounted on a thin member arm preferably a curved thin member such as a stiff wire, the member preferably having opposite ends engageable with respective arms of the tubular body and suitably in apertures in the respective arms.

[0017] Where the skirt comprises a single tubular member, the member may be

mounted to a substantially circular thin member, typically a relatively stiff wire which can be extended over the shorter arm of the tubular body to be supported thereon such that the skirt hangs downwardly and surrounds the upper open end of the tubular body. Suitably opposite slots are provided on or adjacent the tubular body to receive the thin member at opposite diametrical positions and support the skirt.

[0018] Preferably, the sample collection device includes a planar base member

having the opening therein to receive the tubular body and means are provided for closing the opening to prevent escape of collected materials from the collection device. The closing means suitably comprises a planar closure member adapted for sliding engagement with the planar base member.

[0019] The collection device suitably includes a flexible fabric or membrane secured to the planar base member and extending peripherally outwardly therefrom. The planar base member is suitably arranged centrally of the flexible fabric or membrane. [0020]The tubular body and other components associated therewith and the planar member and closure member are suitably formed of a hard wearing material such as steel however the components may also be formed of metal other than steel or of plastics.

[0021 ] Where soil samples are extracted from the ground as described above,

additional processing of the soil samples may be required to break up materials in the soil sample larger than the openings or perforations in the first screening member and provide samples suitable for analysis such as for assessing the organic carbon content. For this purpose the present invention also provides a sieve assembly through which the soil samples collected as above or from another source may be sieved. The sieve assembly comprises at least one sieve comprising a tray in the form of an hollow elongated trough-like body, the base of the body having a series of openings or perforation therein through which materials may be sieved. Soil samples may be deposited into the bodyr and sieving may be effected by applying a heavy or weighted member to the soil samples and moving the member longitudinally back and forth along the base of the body whilst a downward force is applied to the heavy or weighted member to break up materials and force materials of a size smaller than the perforations or openings through the base of the body.

[0022] Most preferably, the base of the body comprises a first planar fine sieve

member and a second planer coarse sieve member juxtaposed with and underlying the first sieve member. Such an arrangement provides support to the fine sieve member and permits materials to be forced through the fine sieve member without damaging the fine sieve member as it is supported by the second sieve member. Preferably the first sieve member comprises a fine mesh typically of 2 mm sized openings. Preferably the second sieve member comprises a coarse mesh such as a woven mesh or perforated plate having typically of 5- 10 mm sized openings. Preferably the first and second sieve members are held in a juxtaposed relationship by having at least the opposite side marginal portions of the sieve members clamped together.

[0023] Preferably the sieve assembly also includes a collector comprising a further tray in the form of an hollow elongated trough-like body in which sieved materials which pass through the at least one sieve member collect. The body of the collector suitably has an imperforate base and side walls. Preferably the body of the at least one sieve member is of a size and configuration which enables it to be partly nested within or stacked on and supported by the body of the collector so that materials forced through the at least one sieve can collect in the collector. Preferably the body of the at least one sieve has outwardly directed flanges which enable it be seated and supported on opposite outwardly directed flanges on the body of the collector. Further the at least one sieve is preferably capable of longitudinal sliding movement relative to the collector.

[0024] For facilitating discharge of materials from the at least one sieve, that is

materials which are comprised of particles which cannot be forced through the base of the sleeve, the at least one sieve is preferably capable of pivoting about a horizontal axis such that it can be pivoted to an inclined position whereby materials therein can be discharged by tipping or pivoting the sieve body to allow discharge of materials from one end thereof under the influence of gravity.

Preferably pivotal movement of the at least one sieve is achieved by providing pivot members on the at least one sieve and pivot stops on the collector with which the pivot members may cooperate to allow for pivoting movement of the at least one sieve. Preferably when the at least one sieve is slid longitudinally relative to the collector, the pivot members thereon can cooperate with the pivot stops. Preferably the pivot members are provided at one end of the at least one sieve and the pivot stops are provided at the corresponding end of the collector.

[0025] Preferably the pivot members comprise opposite pivot pins on opposite sides of the body of the at least one sieve and the pivot stops comprise slots into which the pins may be received and releasably captured. The pivot slots may be define by U-shaped members secured to or at one end of the body of the collector whereby when the body of the at least one sieve is slid longitudinally, the pivot pins can move into and be captured within the slots. Preferably the slots are of width which is similar to the diameter of the pivot pins.

[0026] Preferably the sieve assembly comprises one of more further sieves having a trough-like body similar to that of the at least one sieve but having a single mesh or perforated material in its base with perforations or openings larger than that of the one sieve. Preferably the one or more further sieves are stackable one above the other. Preferably the one or more further sieves is provided with pivot members cooperable with pivot stops on the underlying sieve such that the at least one further sieve can be moved to a position in which it can be tilted or pivoted about a horizontal axis for discharge of materials captured thereon. The pivot stops and pivot members may be of similar configuration to the pivot stops and pivot member on the collector and at least one sieve. Preferably the pivot members are provided intermediate the ends of the or each further sieve which are cooperable with pivot stops provided at a corresponding end of an underlying sieve

[0027] Preferably, the trough-like body of each sieve and the collector is formed so that it may be partly nested with or stacked above and supported by the

immediately underlying body and so as to be slidable longitudinally relative thereto. Each body for this purpose has side walls which are inclined inwardly towards the body. Preferably each body is closed at one end typically by a transversely extending wall or barrier and open at its opposite end to allow for discharge of materials therefrom. Suitably the apparatus also include a support frame on which the collector may be supported for longitudinal sliding movement. The frame suitably includes opposite horizontal elongated frame members or rails on which the trough-like body of the collector may seat. Preferably the elongated frame members are provided with pivot stops and the body of the collector is provided with pivot members adapted to cooperate with the pivot stops when moved longitudinally of the frame in a similar manner to that described above to allow for pivoting of the collector and discharge of sieved materials therefrom. Preferably the pivot stops are provided at one end of the horizontal frame members or rails and the pivot members are provided intermediate the ends of the collector. Pivot stops may also be provided at the end of the collector corresponding to the one end of the horizontal frame members for engagement by pivot members of a sieve supported on the collector. If desired a collection container may be hung from the pivot stops on the collector body for collection of materials discharged from the collector.

Brief Description of Drawings

[0028]Fig. 1 illustrates the apparatus for obtaining soil samples according to an

embodiment of the invention; [0029] Fig. 1 A illustrates a modified form of the apparatus of Fig. 1 ;

[0030]Fig. 2 illustrates a soil extraction tool for use with the apparatus of Fig.1 or Fig.l A;

[0031 ]Fig. 3 illustrates the manner in which the soil sampling apparatus is set up for use;

[0032] Figs. 4, 5 and 6 illustrate the apparatus in different positions as the auger is advanced into the ground;

[0033] Fig. 7 illustrates the manner in which the soil remaining in the tubular body of the soil sampling apparatus after withdrawal of the auger from the body;

[0034] Fig. 8 illustrates the soil collection device at the completion of soil sample collection;

[0035] Fig. 9 is a cross-sectional view of the apparatus for screening the soil

samples;

[0036] Fig. 10 is a perspective cut-away view of part of the screening apparatus for screening soil samples;

[0037] Fig. 1 1 illustrates the underside of the fine screening sieve of the apparatus of Fig. 9 and 10;

[0038] Figs. 12 illustrates a modified form of screening apparatus; and

[0039] Fig. 13 shows the manner in which screened materials may be discharged from the apparatus of Fig. 12.

Description of Embodiments

[0040] Referring to the drawings and firstly to Fig. 1 , there is illustrated the

components of apparatus 10 for obtaining a sample of soil from the ground, the apparatus 10 including a sampling device 1 1 having a main tubular body 12 which is open at each end and which is provided at its upper end with a collar 13 typically formed integrally with or attached to the tubular body 12, the collar 13 having an upper peripheral outwardly angled frustoconical surface 14. Mounted to opposite diametrical sides of the collar 13 are a pair of upstanding brackets 15 which carry a pair of opposite arms 16 and 17 which extend in opposite radial directions relative to the collar 13 and body 12. One of the arms 17 is longer than the other arm 16 for a purpose which will become apparent further below

[0041 ] In addition, both arms 16 and 17 are provided on their upper side and

adjacent the respective brackets 15 with a series of spaced openings 18 and 19 respectively. The openings 18 and 19 are adapted to detachably receive opposite ends 20 and 21 of a thin curved member or wire 22 which carries a downwardly hanging skirt 23 formed of a flexible fabric such as canvas. The arms 16 and 17 can also be engaged by a further member 24 of similar configuration to the member 22 which carries a further skirt 23', the member 24 having ends 20' and 21 ' which can also be engaged with respective openings 18 and 19 in the arms 16 and 17. The skirts 23 and 23' when mounted to arms 16 and 17 by means of the curved members 21 and 21 ' engaging with the openings 18 and 19 oppose each other and cooperate with and overlap each other so that the upper end of the tubular body 12 including the collar 13 can be fully surrounded by the skirts 23 and 23'. As shown, the skirts 23 and 23' extend downwardly below the upper end of the body 12 whilst the brackets 15 which extend above the collar 13 ensure that the upper edges of the skirts 23 and 23' are located above the collar 13.

[0042] In an alternative configuration, the pair of skirts 23 and 23' are replaced by a single annular skirt 25 as shown in Fig 1 A which is provided at its upper end with relatively stiff circular or looped supporting wire 26 contained within a sleeve 27 around the upper end of the skirt 25. To support the sleeve 27 in its required position, the respective brackets 15 are provided with slots 28 which extend inwardly from the outer edges of each bracket 15. The sleeve 27 may be positioned by looping it from above over the longer arm 16 and locating the supporting wire 26 in one slot 28 adjacent the arm 16 and then looping and stretching it over the other arm 17 so that the wire 27 can be located in the opposite slot 28. The skirt 25 will then be supported in a position hanging downwardly and substantially surrounding the upper open end of the tubular body 12.

[0043] The tubular body 12 as shown in Fig 1 , has its inner surface 29 adjacent its lower end angled outwardly and downwardly towards the lower end of the body 12 such that the lower end of the body 12 is tapered to an annular fine edge to assist the body 12 to penetrate the soil into which the body 12 is to be inserted. Alternatively as shown in Fig. 1 A, the lower end 30 of the tubular body 12 is formed with a sawtooth configuration comprising a plurality of teeth 31 . This will enable the body 12 to cut into penetrate the ground when a downward force is applied to the body 12 and the body 1 1 is rotated in opposite directions as described further below.

[0044] The apparatus 10 additionally includes as shown in Fig. 1 , a soil catchment device 31 which comprise a central planar member 32 which in this embodiment comprises a metal plate, the member 32 having a central aperture 33 therein which is of a diameter slightly greater than the external diameter of the tubular body 12 so that the latter may be freely received in and passed through the aperture 33. The member 32 is provided on its upper side and on opposite diametrical sides of the aperture 33 with a pair of retaining arms 34 which are capable of holding a planar closure member 35 over the aperture 33 to close the aperture 33. The arms 34 are typically secured at one end 34' to the member 33 and are free at their opposite ends such that the planar closure member 35 may be inserted under the free ends of the arms 34 and slid over the aperture 33 whereby the arms 34 will apply a resilient force to the member 35 and hold it in position over the aperture 33. The central planar member 32 also acts as a stop to further downward movement of the collar 13 or brackets 15 and thus the tubular body 12 into the soil.

[0045] The member 32 is arranged centrally on and is secured to a flexible sheet or membrane 36 such as by adhesives and/or mechanical fasteners. The central region of the sheet or membrane 36 has an opening therein or terminates outwardly of the aperture 33 such that the aperture 33 is not blocked by the sheet or membrane 36. Typically the sheet or membrane 36 comprises canvas or similar hard wearing material.

[0046] The apparatus 10 additionally includes a high speed power driven auger

assembly typically a combustion engine powered auger assembly 37 comprising an auger 38 having a diameter slightly less than the internal diameter of the tubular body 12 and an internal combustion engine 39 coupled to the auger 38. The auger assembly alternatively may include an electric drive motor rather than a combustion engine. The auger assembly 37 is further provided with handles 40 which facilitate gripping of and support of the auger assembly 37 in an upright attitude. The auger assembly 37 includes indicating means 41 such as a marked line on the auger shaft to indicate the depth of operation of the leading end of the auger 38 so that the operator can ensure that the leading end of the auger 38 does not extend significantly beyond the lower end of the tubular body 12 when the body 12 is at its lowermost position in the ground. This will ensure that only materials within the tubular body 12 are collected.

[0047] For collection of any remaining soil within the tubular body 12 after withdrawal of the auger assembly 37, the apparatus 10 also may include an elongated rotatable hand tool 42 (see Fig, 2) which has an elongated shaft 43 having a handle 44 at one end and a soil lifting device 45 at its opposite end, the device 45 including a plurality of, in this instance, four equi-spaced radially extending blades 46 which are fixed to the lower end of the shaft 43 and which are angled to the plane of rotation of the device 45. Above the blades 46, there are provided a pair of flaps 47 in the shape of a segment of a circle and having an outer diameter substantially the same as the inner diameter of the tubular body 12, the flaps 47 being formed of a flexible material such as rubber, the flaps 47 being fixed at their inner ends to the shaft 43 and extending greater than 180 ^Q so that they overlap each other in circumferential direction.

[0048] For taking a soil sample or samples from a particular area of ground, the

membrane 36 carrying the central guide member 32 is located flat on the ground and the sampling device 1 1 supported by the user in an upright attitude with the lower end of tubular body 12 located in or aligned with the aperture 33 in the member 32 as shown in Fig. 3. If the skirts 23 and 23' are not already attached to the arms 16 and 17, they are attached by means of the ends 20 and 21 and 20' and 21 ' of the members 22 and 24 being located in pairs of apertures 18 and 19 so that the skirts 23 and 23' surround the collar 13 and upper end of the tubular body 12 in the manner shown in Fig. 1 . Alternatively a skirt 25 as shown in Fig 1 A can be mounted to the brackets 15 to surround the upper end of the tubular body 12. The auger assembly 37 is then positioned as shown in Fig. 3 so that the auger 38 extends into the tubular body 12 with the lower end thereof sitting on the ground within the aperture 33 in the central member 32 with the user using the handles 40 to hold the auger assembly 37 in an upright attitude. Alternatively, the auger 38 is positioned within the tubular body 12 prior to the body 12 being positioned in its upright attitude where it locates with the aperture 33 in the member 32.

[0049]The engine 39 of the auger assembly 37 is then operated to rotate the

auger 38 at high speed which will cause it to be advanced into the ground as shown in Fig. 4. During this operation, the longer arm 1 6 of the sampling device 1 1 abuts usually the thigh of the user which acts as a stop to prevent or limit rotation of the body 12 and a downward force applied by the handles 16 and 17 to advance the tubular body 12 into the soil. The tubular body 12 either follows the auger 38 as it is advanced into the ground or an impact force may be applied to the upper end of the tubular body 12. As the auger 38 is rotated at a high speed, soil within the body 12 will be conveyed through the tubular body 12 upwardly by the auger flights to exit the tubular body 12 at the upper end thereof. The skirts 23 and 23' ensure that materials 42 which are thrown radially outwardly will on hitting the skirts 23 and 23' fall

downwardly to collect on the membrane 36 and/or member 32 below.

Directing of materials 42 downwardly for collection is further enhanced by the inclined upper surface 14 of the collar 13 which will also tend to direct materials downwardly onto the membrane 36 and/or member 31 .

[0050] As the auger assembly 37 is continued to be operated, the tubular

body 12 is further forced downwardly or simply advances with the auger 38 into the soil with this movement being facilitated by the tapering lower end 29 of the body 12. Alternatively where the lower end of the body 12 is provided with a plurality of teeth 31 as shown in Fig 1 A, the tubular body 12 can be rotated in opposite directions so that the teeth 31 penetrate the ground and the body 12 advances downwardly into the soil. As the collar 13 and upper end of the tubular body 12 approach the ground surface 43, the skirts 23 and 23' (or skirt 25) will on contacting the surface 43 crumple or collapse to some extent but still act as a barrier to soil thrust radially outwardly of the body 12 and ensure that such materials collect on the membrane 36 and/or member 32 as shown in Fig. 4.. [0051 ] When the collar 13 of the tubular body 12 and/or brackets 15 reaches the ground level 43 it or they will abut the member 32 and/or ground so that the collar 13 and body 12 will be prevented from further downward movement as shown in Fig. 5. During operation of the auger assembly 37, its position is monitored by the user using the indicator 41 so that the user can see the depth of its operation. When the collar 13 abuts the member 32 thereby stopping further downward movement of the body 12 and soil discharge by the auger 38 ceases, the auger assembly 37 is then stopped and can be removed from the body 12. This means that a sample of soil substantially equal to the volume of the tubular body 12 below the collar 13 should have been collected.

[0052] For accurate collection of the sample of soil, any remaining soil or

materials 48 within the tubular body 12 can be removed and added to the already collected materials by using the tool 42 as shown in Fig. 7. This tool 42 is inserted longitudinally into the body 12 and lowered until the device 45 is sitting on the top of the remaining materials in the body 12. The tool 42 is then rotated by hand by using the handle 44. This will cause the blades 46 to penetrate the materials 48 due to their angle of attack and cause the flaps 47 to locate under the materials 48 in the position shown in Fig. 6. The tool 42 can then be lifted out of the tubular body 12 with the flaps 47 extending substantially across the full cross-section of the tubular body 12 carrying the materials 48 which can be deposited onto the membrane 36. The device 1 1 can then be withdrawn from the ground using the handles 16 and 17 if required. The soil sample size taken from different locations therefore remains consistent and precise

[0053] The closure member 35 may then be slid under the arms 34 and over the aperture 33 in the manner shown in Fig. 8. The corners of the membrane 36 may then be folded in as indicated by the arrows in Fig. 8 or otherwise manipulated so that the collected soil sample can be carried and transferred for further processing or analysis.

[0054] The method and apparatus described above are particularly suited to

obtaining soil samples for analysis for obtaining an indication of the carbon content in soil for example for the purposes of paying remuneration in a program which rewards carbon dioxide sequestration. Such programs require the relatively accurate testing of soil samples to assess the organic carbon content of the soil and then calculating the carbon dioxide equivalent per hectare (or per acre) increase from a previous test. For this purpose the method and apparatus of the invention may be applied to the taking a number of samples of soil from random locations in an area such as a predetermined field of paddock or other area of ground. The location for soil samples to be taken may be determined randomly and preferably at a distance not greater than 10% of the distance from the geometric centre of each nominated area. Subsequent test samples may then be obtained from locations at a random distance, and in a random direction from previous tests. Of course it will be appreciated that there are many different means by which the random locations for taking soil samples in a predetermined area may be determined. The outer diameter of the tubular body 12 equates to a calculated ground area and this area consequently bears a known mathematic relationship to the paddock area from which the sample is taken.

[0055] After taking a sample of soil using the method and apparatus described above, the sample is screened to allow for removal of all fibrous material such as plant and animal material not yet decomposed as well as rocks, stones or other large particles. For this purpose, a number of soil samples taken from random locations in a particular paddock can be place in rotary mixer to intermix to form an homogenous composite which can be worked through a screening apparatus or sieve to remove fibrous materials and large particles. A suitable screening and soil collection apparatus 49 for this purpose is shown in Figs. 9 to 1 1 . The apparatus 49 includes an elongated collection tray 50 and course and fine screening trays 51 and 52, the trays 51 , 52 and 50 being capable of being "piggy-backed" one above the other and releasably coupled together.

[0056] The collection tray 50 comprises a hollow trough-like channel shaped body 53 which is closed at one end 54 by a transverse barrier wall and open at its opposite end 55 and has opposite outwardly angled side walls 56 extending upwardly from a base wall 57 and terminating in upper outwardly directed flanges 58. The walls 56 and base 57 of the body 53 are all imperforate. [0057] The fine screening tray 52 is of a similar configuration in cross-section to the tray 50 being of trough-like form comprising a body 59 having outwardly angled side walls 60 with outwardly directed flanges 61 on opposite sides adjacent their lower ends which can seat on the flanges 58 of the body 53 and so that the base 62 of the body 59 locates between the side walls 56. The base 62 comprises an upper fine screen or mesh 63 overlying and juxtaposed with a course screen or mesh 64 as can be seen in Fig. 1 1 , the latter supporting the fine screen or mesh 64. The opposite longitudinal marginal portions of the coarse and fine screens of mesh 63 and 64 are clamped together between Z- sectioned members 65 and inwardly directed base flanges 60' at the lower ends of the side walls 60, the member 65 being secured to the flanges 60' by rivets or other fasteners 66. The Z-sectioned members 65 define the outwardly directed flanges 61 and the side walls 60 also have outwardly directed flanges 60" at their upper ends.

[0058] The course screening tray 51 is of a similar configuration in cross-section to the tray 52 comprising a body 67 having outwardly angled side walls 68 with flanges 69 on opposite sides adjacent their lower ends which can seat on the flanges 61 " of the body 52 and so that the base 70 of the body 67 locates between the side walls 60. The base 70 comprises a course screen or mesh 71 preferably similar to the course screen or mesh 64 of the tray 52. The course screen or mesh preferably is of a woven construction as shown more clearly in Fig. 1 1 but may be formed of perforated pressed metal plate. The mesh 71 is secured by a similar arrangement to that described for securing the mesh or screens 63 and 64 of the tray 52.

[0059] A soil sample collected as above and required for carbon content analysis is placed into the upper tray 51 and onto the screen 70. Finer materials will pass through the screen 70 and collect on the base 62 of the underlying tray 52 or in the tray 50 whilst larger materials such as plant and animal matter or other fibrous materials and large particles will collect on the screen 70 for removal by hand. A force may be applied to the remaining materials on the base 70 to break up larger components if possible to allow passage through the screen 70. A force to the materials may typically be applied using a roller or weighted member which can be moved back and forth over the base of a selected tray to break up larger particles and force materials capable of passing thorough the apertures or perforations in the screen 70. When no further materials can be forced through the screen 70, the tray 51 is removed. A similar procedure is followed for materials gathering on the base 62 of the tray 52 with finer materials passing therethrough or being forced therethrough by a suitable tool as above. Thus the screened materials of the required size to enable them to be analysed collect in the tray 50.

[0060] In a modified configuration, the respective trays may be constructed so that they are capable of pivoting about a horizontal axis for discharge of materials from the tray namely materials whose particle size prevents them from passing through the base of that tray. The sieving apparatus 72 shown in Figs. 12 and 13 is similar to the apparatus 49 and accordingly like components have been given like numerals. In this embodiment as shown in Figs. 1 1 , there is provided a frame assembly 73 for supporting the trays 50, 51 and 52, the frame assembly 73 having spaced apart rigid U-shaped legs 74 which are joined by elongated side members or rails 75 which are fixed to opposite upright members of the legs 74 and which are spaced apart a distance such that respective side flanges 76 provided at the lower end of the walls 53 of the collection tray 50 may seat thereon. In this embodiment, the apparatus 72 can also include an additional coarse screening tray 77 as show shown in Fig. 12 which is similar to the tray 51 but which has a coarser screen material in its base. The tray 77 is positioned above and seats on the tray 51 in a similar manner to the seating of the tray 51 on the tray 52.

[0061 ] The side frame members 75 are also provided at one end with respective pivot stops 78 in the form of U-shaped members 79 which lie in a vertical plane and which are open in a direction towards the trays when seated on the frame assembly 73. Each tray 50, 51 , 52 and 77 is also provided with similar U-shaped pivot stop members 79 at their ends corresponding to the end of the frame assembly 73 carrying the pivot stops 78.

[0062] Each tray 50, 51 , 52 and 77 is additionally provided with respective pivot members in the form of pivot pins 80 which are fixed to the trays 50, 51 , 52 and 77 and extend laterally to each side of the tray 50, 51 , 52 and 77. The base collection tray 50 is provided with the pivot pins 80 adjacent the open end thereof whilst the remaining trays have their pivot pins 80 positioned intermediate their opposite ends. Each pivot pin 80 is capable of being received in a U-shaped stop member 79 of an underlying tray or frame 73) when a tray is slid longitudinally to define a transverse pivotal axis for a tray. A materials collection container 81 (shown in dotted outline in Fig. 13) can also be hung from the U-shaped members 79 for collection of materials therein as described below.

[0063] In this embodiment, the sieving apparatus 72 comprises four trays 50, 51 ,52 and 77 comprising the base collection tray 50 and three further sieving trays 51 , 52 and 77 which can be arranged so that base tray 50 seats on the frame assembly 72 and the other trays 51 , 52 and 77 seating on the immediate underlying tray. The uppermost tray 77 has a base with openings or perforations of the largest size typically 10mm, the next tray 52 having smaller openings typically 5 mm and the lowermost tray 51 having a base comprising juxtaposed screens with the smallest openings typically approximately 2 mm in size. The above dimensions however may be varied depending upon the application.

[0064] Material to be sieved is deposited into the uppermost tray 77 and worked through the openings therein and any materials of larger size which cannot pass through the sieve openings therein will remain in the upper tray 77. These materials may be discharged by sliding the uppermost tray 77 longitudinally until its pivot pins 80 locate in the pivot stop members 79 which prevents further sliding movement of the tray 77 whereupon the tray 77 can be pivoted or tipped about a transverse pivot axis defined by the pivot pins 80 so that the collected materials can be discharged from the open end of the tray 77 as shown in Fig. 13. If desired, a collection container 81 can be hung from the U-shaped members 78 of the tray 77 so that when the tray 77 is pivoted, materials on the tray 77 can be collected in the container 81 or those materials may be simply discharged onto the ground. The uppermost tray 77 can then be removed and the procedure described above repeated for the second tray 51 and then the third tray 52. Materials forced through the third tray 52 comprise materials of a size less than the size of the openings in the tray 52 and are of a size to enable analysis for organis carbon content calculation in apparatus such as that disclosed in my aforesaid International application.

[0065] A series of screened samples of soil collected from random locations in a field or paddock may be mixed together in a suitable mixing device for example a rotating mixing device and a soil sample to be tested may be extracted from the mixed soil samples, that soil sample being the average of the soil samples over the whole field or paddock from which the samples have been taken. Suitable testing such as that described in my aforementioned International patent application may be carried out on the soil sample to obtain an assessment of the organic carbon content of the soil sample which is representative of the carbon content of soil in the whole area being tested. Thus the organic carbon content of the blended and screened tested sample allows the mathematic determination of the organic carbon content of the paddock down to the nominated sampling depth.

[0066] The term "soil" as used throughout the specification and claims includes earth or ground of any form and any mixture of organic and inorganic materials.

[0067] It will be appreciated that the apparatus of the invention may be in many different configurations other than that illustrated and described to perform the method of the invention. The mounting arrangement for the skirt members 23 may be other than that described and illustrated in the embodiment and other means may be provided for preventing or limiting rotation of the tubular body such as an anchoring device. The closure member 35 may be attached to the plate 32 for example through a hinge so that it can move between positions in which it opens or closes the opening 33.

[0068] Typically, the tubular body 12 has an outer diameter of 1 15mm and in

operation, the body 12 penetrates 0.5 m into the soil or less if desired. The length of the body 12 however may be increased for special applications. The collector membrane 36 is typically approximately one metre square however this can also be of different sizes.

[0069] For transportation purposes, the frame 73 of the sieve assembly 72 may be inverted and the respective trays piggy-backed together with the lowermost tray spaning and being supported on the rails or members 75 through the flanges 76 with all trays being located internally of each U-shaped leg 74. Whilst the trays for the sieve assemblies described preferably have a base and side walls which are angled outwardly from the base to an open upper side, the trays may be of other cross-sectional shapes. Typically a sieve assembly is made up of a single collection tray and three sieving trays but it may include more or less trays. Furthermore the respective trays may have openings or combinations of openings of any desired opening or perforation size depending upon the application. The sieve assemblies described may also be used in applications other than for sieving soil samples obtained from the apparatus and method described in relation to Figs. 1 to 8.

[0070] Any reference to prior art herein is not to be taken as an

acknowledgement that such art constitutes common general knowledge. Further the terms "comprising" or "comprises" as used throughout the specification and claims are taken to specify the presence of the stated features, integers and components referred to but not preclude the presence or addition of one or more other feature/s, integer/s, component/s or group thereof.

[0071 ] Whilst the above has been given by way of illustrative embodiment of the invention, all such variations and modifications thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein defined in the appended claims.